Art of cracking hydrocarbons



Coungusm Filed. March 20, 1923 Patented Aug. 21, 1923.

UNITEDVSTATES PATENT OFFICE.

FRANK A. HOWARD, F ELIZABETH, NEW JERSEY, ASSIGNOR 1'0 STANDARD OIILDE"VELOPMEN'J. COMPANY, A CORPORATION OF DELAWARE.

ART OF CRACKING LEYDROGARBONS. 1

Application filed March 20, 1923. Serial No. 626,264.

This invention relates to the art of pyrolytic conversion ofhydrocarbons into products of lower boiling point, and will befullyunderstood from the following description, taken in connection with theaccompanylng drawing which represents semi-diagramatically one form ofapparatus contemplated in the invention.

In the Patent No. 1,415,232 to Ellis, there is set forth a process inwhich an oil is brought up to decomposing temperature by passing througha heated zone and is then allowed to crack while passing at a slowerrate through row by a connection 4 leading to an upper row of tubes 5.The number of rows provided may be as preferred, but for usual conditons two rows with the tubes in staggered positions is desirable. Sucharrangement qulte completely presents surfaces intercepting ra d1antheat rays from the furnace chamber, while allowing the hotcombustiongases to freely pass up beyond. From the lower 0011, a pipe 6 leads to avaporizing chamber or still 7 This may be of any desired form, forinstance of water-tube boiler type, or a simple shell still. A tardraw-off pipe 8 is connected at the lowest part, and from the top of thestill a vapor line or pipe 9 leads to a second coil B in the furnacechamber 1. This coil may be constructed along the same general lines asthe first coil and be made up of a pluralitypf rows of tubes 10according to the capacity desired, the spacing of the tubes being suchas to allow a good exposure to the combustion gases on their way to theexit fiues F. From this upper coil a discharge pipe 11 leads to anenlarged passageway or drum 12, which may conveniently be placed in thetop of the same furnace-setting and lagged or heat-insulated on top, soas to maintain the temperature desired. The drum may, however, be set inany other way desired, so long as 1t 1s prepared to maintainthetemperature of its contents without'substantial decline.

From the enlarged passageway or drum 12 a vapor line or pipe 13 leads,preferably with a sli ht downward gradient, to a suitable recti yingdevice 14, which may be a dephlegmat-or or fractionating tower asdesired. A vapor line 15 from the top of the rectifier 14 connects,through a suitable cooled con denser 15, with a receiving drum 16,having valve-controlled drain-line 17 and gas-release 18 as usual. Apipe 19 with pump 20 connects the lower part of the receiving tank withthe upper part of the rectifier, for a purpose to be referred to later,and a reflux-pipe 21, with a pump 22 where necessary, leads from thelower part of the rectifier back to the still 7 In carrying out myprocess, the oil to be cracked is fed into the system by pipe 2.Advantageously such oil may be a crude from which the light constituentshave been removed. Passing through the lower coil A, the oil isdischarged into the still 7, having been heated-sufliciently to allowsubstantial vaporization of the constituents desired. Such additionalheat as is necessary to efi'ect the degree of vaporization wanted isprovided by firing the still 7 in the usual manner. In

this still it is the aim to take off the constituents most suitable forcracking, these being forwarded in vapor form to the coil B. Thedistillation is thus carried to a low percentage pitch bottom, as heavyas can be handled, the bottoms or residue being drawn oif, continuouslyor intermittently as desired, through the tar line 8. In this way, oilsof any practicable content of crackable constituents may be efficientlyhandled, irrespective of asphalt or coke-forming contents, suchmaterials being separated from the crackable constituents and eliminatedbefore the cracking stage, and by eliminating such materials seriouscoke troubles in the cracking operation are avoided. The .pressure inthe still 7 may be as low as is consistent with a good delivery rate ofvapors on through the coil B, and depending upon the stock operated uponmay in general lie between 5 and 150 pounds per square inch. Asindicated, the vapors proceed to the coil B and passing therethrough areraised to a temperature of 875975 F. The position of this coil B is suchthat it is shielded by the lower coil A, the coil A in fact beingdesigned as a screen interposed between the coil B and the furnace, toprotect coil B against the radiant heat of the furnace. The coil Ahandling the feed oil at an adequate velocity on its way to the still 7absorbs the radiant heat, it being harmlessly directed to raising thetemperature of and partly vaporizing the oil on its way to the still.The heat effective. on the coil 13 is thus limited to the mild andrelatively uniform heat of the combustion gases.

Entering the drum 12 from the coil B, the vapors are passed along at asuitable rate, the inlet preferably being arranged at one end and theoutlet at the opposite end, and the temperature being maintained ingeneral at 825950 F., a yield of 15-30% of gasoline I may be directlyobtained.

The pressure in the drum 12 does notneed to be high, only sufiicient tomaintain a suitable throughput, and may be for instance from 15 up to150 pounds per square inch.

From the drum 12, the vapors proceed to the rectifier 1 1 where thegasoline constituents are sorted out and forwarded to the condenser15and receiving drug 16. To facilitate such rectification, condensateis, drawn off from the receiver 16 and is forced by the pump 20 into theupper part of the rectifier and passing down countercurrent to thevapor, washes and fractionates it. The heavy reflux from the bottom ofthe rectifier, also that draining down from the vapor line ,13 by reascnof its downward slope, is returned through a suitable trap 23 and pipe21 to the still 7 for recycling. Where desired, instead of returning theheavy condensate from the vapor line 13 to the still as mentioned, itmay instead be drawn off aside by a pipe 24.

Vhile I have described my invention by reference to certain specificdetails, it will be understood that this is for the purpose of makingthe invention clear, and is not limitative. And the invention is to beconsidered as limited only as defined in the following claims, in whichit is my intention to claim all inherent novelty as broadly as the priorart permits.

What I claim is:

1. Apparatus of the character described, which comprises a furnace, aheating coil in said furnace located as a screen to absorb radiant heat.a distillation chamber into which said coil discharges, another heatingcoil in said furnace screened by the firstmentioned coil and receivingvapors from the distillation chamber, an enlarged passageway into whichthe last-mentioned coil discharges, means for maintaining thetemperature in the enlarged passageway without substantial decline, avaporline leading from said enlarged passageway and having adownwardslope therefrom. a rectifier for the vapors, a vapor line from the topof said rectifier, a c ndenser on said vapor line, a

tankfor receiving condensate, means for returning condensate from saidtank into the top of the rectifier, and means for returning refiux fromthe bottom of the rectifier to the distillation chamber.

2. Apparatus of the character described, which comprises a furnace, aheating coil in said furnace located as a screen to absorb radiant heat,a distillation chamber into which said coil discharges, another heatingcoil in said furnace screened by the first-mentioned coil and receivingvapors from the distillation chamber, an enlarged passageway into whichthe last-mentioned coil discharges, means for maintaining thetemperature in the enlarged passageway without substantial decline, avapor line leading from said enlarged passageway and having a downwardslope therefrom, a rectifier for the vapors, a vapor line from the topof said rectifier, a condenser on said vapor line, and means forreturning condensate into the top of the rectifier;

3. Apparatus of the character described,

which comprises a furnace, a heating coil in said furnace located as ascreen to absorb radiant heat, a distillation chamber into thecombination of aheating coil located as a screen to absorb radiant heat,a distillation chamber into which said coil discharges, another heatingcoil screened by the firsbmentioned coil and receiving vapors from thedistillation chamber, an enlarged passageway into which thelast-mentioned coil discharges, means for maintaining the temperature in.the enlarged passageway without substantial decline, and means forrectifying vapors from said enlarged passageway.

5. In apparatus of the character described, the combination of a heatingcoil located as a screen to absorb radiant heat, a distillation chamberinto which said coil discharges, another heating coil screened by thefirst-mentioned coil and receiving vapors from the distillation chamber,an enlarged passageway into which the last-mentioned coil discharges,and means for maintaining the temperatiire in the enlarged passagewaywithout substantial decline.

6. In apparatus of the character described, the combination of a heatingcoil located as a screen to absorb radiant heat, a distillation chamberinto which said coil discharges, another heating coil screened solely bythe firstmentioned coil. and a vapor line from the chaniher to thelast-mentioned heating coil.

7. In apparatus of the character described,

the cmnhination of a furnace, a heating coil 5 arranged to receiveradiant heat from the furnace. a cracking passageway shielded fromradiant heat solely by said coil, means for separating asphalticsubstances from the hydrocarbon material which has traversed the heatingcoil, and means for passing vapors from the separating means to thecracking passageway.

FRANK A. HOWARD.

